Quick-connect prosthetic heart valve and methods

ABSTRACT

A heart valve prosthesis that can be quickly and easily implanted during a surgical procedure is provided. The prosthetic valve has a base stent that is deployed at a treatment site, and a valve component configured to quickly connect to the base stent. The base stent may take the form of a self- or balloon-expandable stent that expands outward against the native valve with or without leaflet excision. The valve component has a non-expandable prosthetic valve and a self- or balloon-expandable coupling stent for attachment to the base stent, thereby fixing the position of the valve component relative to the base stent. The prosthetic valve may be a commercially available to valve with a sewing ring and the coupling stent attaches to the sewing ring. The system is particularly suited for rapid deployment of heart valves in a conventional open-heart surgical environment. A catheter-based system and method for deployment is provided.

The present application claims priority under 35 U.S.C. §119(e) to U.S.provisional application No. 61/139,398 filed Dec. 19, 2008.

FIELD OF THE INVENTION

The present invention generally relates to prosthetic valves forimplantation in body channels. More particularly, the present inventionrelates to prosthetic heart valves configured to be surgically implantedin less time than current valves.

BACKGROUND OF THE INVENTION

In vertebrate animals, the heart is a hollow muscular organ having fourpumping chambers as seen in FIG. 1: the left and right atria and theleft and right ventricles, each provided with its own one-way valve. Thenatural heart valves are identified as the aortic, mitral (or bicuspid),tricuspid and pulmonary, and are each mounted in an annulus comprisingdense fibrous rings attached either directly or indirectly to the atrialand ventricular muscle fibers. Each annulus defines a flow orifice.

The atria are the blood-receiving chambers, which pump blood into theventricles. The ventricles are the blood-discharging chambers. A wallcomposed of fibrous and muscular parts, called the interatrial septumseparates the right and left atria (see FIGS. 2 to 4). The fibrousinteratrial septum is a materially stronger tissue structure compared tothe more friable muscle tissue of the heart. An anatomic landmark on theinteratrial septum is an oval, thumbprint sized depression called theoval fossa, or fossa ovalis (shown in FIG. 4).

The synchronous pumping actions of the left and right sides of the heartconstitute the cardiac cycle. The cycle begins with a period ofventricular relaxation, called ventricular diastole. The cycle ends witha period of ventricular contraction, called ventricular systole. Thefour valves (see FIGS. 2 and 3) ensure that blood does not flow in thewrong direction during the cardiac cycle; that is, to ensure that theblood does not back flow from the ventricles into the correspondingatria, or back flow from the arteries into the corresponding ventricles.The mitral valve is between the left atrium and the left ventricle, thetricuspid valve between the right atrium and the right ventricle, thepulmonary valve is at the opening of the pulmonary artery, and theaortic valve is at the opening of the aorta.

FIGS. 2 and 3 show the anterior (A) portion of the mitral valve annulusabutting the non-coronary leaflet of the aortic valve. The mitral valveannulus is in the vicinity of the circumflex branch of the left coronaryartery, and the posterior (P) side is near the coronary sinus and itstributaries.

The mitral and tricuspid valves are defined by fibrous rings ofcollagen, each called an annulus, which forms a part of the fibrousskeleton of the heart. The annulus provides peripheral attachments forthe two cusps or leaflets of the mitral valve (called the anterior andposterior cusps) and the three cusps or leaflets of the tricuspid valve.The free edges of the leaflets connect to chordae tendineae from morethan one papillary muscle, as seen in FIG. 1. In a healthy heart, thesemuscles and their tendinous chords support the mitral and tricuspidvalves, allowing the leaflets to resist the high pressure developedduring contractions (pumping) of the left and right ventricles.

When the left ventricle contracts after filling with blood from the leftatrium, the walls of the ventricle move inward and release some of thetension from the papillary muscle and chords. The blood pushed upagainst the under-surface of the mitral leaflets causes them to risetoward the annulus plane of the mitral valve. As they progress towardthe annulus, the leading edges of the anterior and posterior leafletcome together forming a seal and closing the valve. In the healthyheart, leaflet coaptation occurs near the plane of the mitral annulus.The blood continues to be pressurized in the left ventricle until it isejected into the aorta. Contraction of the papillary muscles issimultaneous with the contraction of the ventricle and serves to keephealthy valve leaflets tightly shut at peak contraction pressuresexerted by the ventricle.

Various surgical techniques may be used to repair a diseased or damagedvalve. In a valve replacement operation, the damaged leaflets areexcised and the annulus sculpted to receive a replacement valve. Due toaortic stenosis and other heart valve diseases, thousands of patientsundergo surgery each year wherein the defective native heart valve isreplaced by a prosthetic valve, either bioprosthetic or mechanical.Another less drastic method for treating defective valves is throughrepair or reconstruction, which is typically used on minimally calcifiedvalves. The problem with surgical therapy is the significant insult itimposes on these chronically ill patients with high morbidity andmortality rates associated with surgical repair.

When the valve is replaced, surgical implantation of the prostheticvalve typically requires an open-chest surgery during which the heart isstopped and patient placed on cardiopulmonary bypass (a so-called“heart-lung machine”). In one common surgical procedure, the diseasednative valve leaflets are excised and a prosthetic valve is sutured tothe surrounding tissue at the valve annulus. Because of the traumaassociated with the procedure and the attendant duration ofextracorporeal blood circulation, some patients do not survive thesurgical procedure or die shortly thereafter. It is well known that therisk to the patient increases with the amount of time required onextracorporeal circulation. Due to these risks, a substantial number ofpatients with defective valves are deemed inoperable because theircondition is too frail to withstand the procedure. By some estimates,about 30 to 50% of the subjects suffering from aortic stenosis who areolder than 80 years cannot be operated on for aortic valve replacement.

Because of the drawbacks associated with conventional open-heartsurgery, percutaneous and minimally-invasive surgical approaches aregarnering intense attention. In one technique, a prosthetic valve isconfigured to be implanted in a much less invasive procedure by way ofcatheterization. For instance, U.S. Pat. No. 5,411,552 to Andersen etal. describes a collapsible valve percutaneously introduced in acompressed state through a catheter and expanded in the desired positionby balloon inflation. Although these remote implantation techniques haveshown great promise for treating certain patients, replacing a valve viasurgical intervention is still the preferred treatment procedure. Onehurdle to the acceptance of remote implantation is resistance fromdoctors who are understandably anxious about converting from aneffective, if imperfect, regimen to a novel approach that promises greatoutcomes but is relatively foreign. In conjunction with theunderstandable caution exercised by surgeons in switching to newtechniques of heart valve replacement, regulatory bodies around theworld are moving slowly as well. Numerous successful clinical trials andfollow-up studies are in process, but much more experience with thesenew technologies will be required before they are completely accepted.

Accordingly, there is a need for an improved device and associatedmethod of use wherein a prosthetic valve can be surgically implanted ina body channel in a more efficient procedure that reduces the timerequired on extracorporeal circulation. It is desirable that such adevice and method be capable of helping patients with defective valvesthat are deemed inoperable because their condition is too frail towithstand a lengthy conventional surgical procedure. The presentinvention addresses these needs and others.

SUMMARY OF THE INVENTION

Various embodiments of the present application provide prosthetic valvesand methods of use for replacing a defective native valve in a humanheart. Certain embodiments are particularly well adapted for use in asurgical procedure for quickly and easily replacing a heart valve whileminimizing time using extracorporeal circulation (i.e., bypass pump).

In one embodiment, a method for treating a native aortic valve in ahuman heart to replaces the function of the aortic valve, comprises: 1)accessing a native valve through an opening in a chest; 2) advancing anexpandable base stent to the site of a native aortic valve, the basestent being radially compressed during the advancement; 3) radiallyexpanding the base stent at the site of the native aortic valve; 4)advancing a valve component within a lumen of the base stent; and 5)expanding a coupling stent on the valve component to mechanically coupleto the base stent in a quick and efficient manner.

In one variation, the base stent may comprise a metallic frame. In oneembodiment, at least a portion of the metallic frame is made ofstainless steel. In another embodiment, at least a portion of themetallic frame is made of a shape memory material. The valve member maytake a variety of forms. In one preferred embodiment, the valvecomponent comprises biological tissue. In another variation of thismethod, the metallic frame is viewed under fluoroscopy duringadvancement of the prosthetic valve toward the native aortic valve.

The native valve leaflets may be removed before delivering theprosthetic valve. Alternatively, the native leaflets may be left inplace to reduce surgery time and to provide a stable base for fixing thebase stent within the native valve. In one advantage of this method, thenative leaflets recoil inward to enhance the fixation of the metallicframe in the body channel. When the native leaflets are left in place, aballoon or other expansion member may be used to push the valve leafletsout of the way and thereby dilate the native valve before implantationof the base stent. The native annulus may be dilated between 1.5-5 mmfrom their initial orifice size to accommodate a larger sized prostheticvalve.

In accordance with a preferred aspect, a prosthetic heart valve systemcomprises a base stent adapted to anchor against a heart valve annulusand defining an orifice therein, and a valve component connected to thebase stent. The valve component includes a prosthetic valve definingtherein a non-expandable, non-collapsible orifice, and an expandablecoupling stent extending from an inflow end thereof. The coupling stenthas a contracted state for delivery to an implant position and anexpanded state configured for outward connection to the base stent. Thebase stent may also be expandable with a contracted state for deliveryto an implant position adjacent a heart valve annulus and an expandedstate sized to contact and anchor against the heart valve annulus.Desirably, the base stent and also the coupling stent are plasticallyexpandable.

In one embodiment, the prosthetic valve comprises a commerciallyavailable valve having a sewing ring, and the coupling stent attaches tothe sewing ring. The contracted state of the coupling stent may beconical, tapering down in a distal direction. The coupling stentpreferably comprises a plurality of radially expandable struts at leastsome of which are arranged in rows, wherein the distalmost row has thegreatest capacity for expansion from the contracted state to theexpanded state. Still further, the strut row farthest from theprosthetic valve has alternating peaks and valleys, wherein the basestent includes apertures into which the peaks of the coupling stent mayproject to interlock the two stents. The base stent may include aplurality of radially expandable struts between axially-oriented struts,wherein at least some of the axially-oriented struts have upperprojections that demark locations around the stent.

A method of delivery and implant of a prosthetic heart valve system isalso disclosed herein, comprising the steps of

-   -   advancing a base stent to an implant position adjacent a heart        valve annulus;    -   anchoring the base stent to the heart valve annulus;    -   providing a valve component including a prosthetic valve having        a non-expandable, non-collapsible orifice, the valve component        further including an expandable coupling stent extending from an        inflow end thereof, the coupling stent having a contracted state        for delivery to an implant position and an expanded state        configured for outward connection to the base stent;    -   advancing the valve component with the coupling stent in its        contracted state to an implant position adjacent the base stent;        and    -   expanding the coupling stent to the expanded state in contact        with and connected to the base stent.

The base stent may be plastically expandable, and the method furthercomprises advancing the expandable base stent in a contracted state tothe implant position, and plastically expanding the base stent to anexpanded state in contact with and anchored to the heart valve annulus,in the process increasing the orifice size of the heart valve annulus byat least 10%, or by 1.5-5 mm. Desirably, the prosthetic valve of thevalve component is selected to have an orifice size that matches theincreased orifice size of the heart valve annulus. The method may alsoinclude mounting the base stent over a mechanical expander, anddeploying the base stent at the heart valve annulus using the mechanicalexpander.

One embodiment of the method further includes mounting the valvecomponent on a holder having a proximal hub and lumen therethrough. Theholder mounts on the distal end of a handle having a lumen therethrough,and the method including passing a balloon catheter through the lumen ofthe handle and the holder and within the valve component, and inflatinga balloon on the balloon catheter to expand the coupling stent. Thevalve component mounted on the holder may be packaged separately fromthe handle and the balloon catheter. Desirably, the contracted state ofthe coupling stent is conical, and the balloon on the balloon catheterhas a larger distal expanded end than its proximal expanded end so as toapply greater expansion deflection to the coupling stent than to theprosthetic valve.

In the method where the coupling stent is conical, the coupling stentmay comprise a plurality of radially expandable struts at least some ofwhich are arranged in rows, wherein the row farthest from the prostheticvalve has the greatest capacity for expansion from the contracted stateto the expanded state.

The method may employ a coupling stent with a plurality of radiallyexpandable struts, wherein a row farthest from the prosthetic valve hasalternating peaks and valleys. The distal end of the coupling stent thusexpands more than the rest of the coupling stent so that the peaks inthe row farthest from the prosthetic valve project outward intoapertures in the base stent. Both the base stent and the coupling stentmay have a plurality of radially expandable struts betweenaxially-oriented struts, wherein the method includes orienting thecoupling stent so that its axially-oriented struts are out of phase withthose of the base stent to increase retention therebetween.

Another aspect described herein is a system for delivering a valvecomponent including a prosthetic valve having a non-expandable,non-collapsible orifice, and an expandable coupling stent extending froman inflow end thereof, the coupling stent having a contracted state fordelivery to an implant position and an expanded state. The deliverysystem includes a valve holder connected to a proximal end of the valvecomponent, a balloon catheter having a balloon, and a handle configuredto attach to a proximal end of the valve holder and having a lumen forpassage of the catheter, wherein the balloon extends distally throughthe handle, past the holder and through the valve component. In thesystem, the prosthetic valve is preferably a commercially availablevalve having a sewing ring to which the coupling stent attaches.

The contracted state of the coupling stent in the delivery system may beconical, tapering down in a distal direction. Furthermore, the ballooncatheter further may include a generally conical nose cone on a distalend thereof that extends through the valve component and engages adistal end of the coupling stent in its contracted state. Desirably, thehandle comprises a proximal section and a distal section that may becoupled together in series to form a continuous lumen, wherein thedistal section is adapted to couple to the hub of the holder to enablemanual manipulation of the valve component using the distal sectionprior to connection with the proximal handle section. Preferably, theballoon catheter and proximal handle section are packaged together withthe balloon within the proximal section lumen.

Alternatively, the valve component mounted on the holder is packagedseparately from the handle and the balloon catheter.

A further understanding of the nature and advantages of the presentinvention are set forth in the following description and claims,particularly when considered in conjunction with the accompanyingdrawings in which like parts bear like reference numerals.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be explained and other advantages and featureswill appear with reference to the accompanying schematic drawingswherein:

FIG. 1 is an anatomic anterior view of a human heart, with portionsbroken away and in section to view the interior heart chambers andadjacent structures;

FIG. 2 is an anatomic superior view of a section of the human heartshowing the tricuspid valve in the right atrium, the mitral valve in theleft atrium, and the aortic valve in between, with the tricuspid andmitral valves open and the aortic and pulmonary valves closed duringventricular diastole (ventricular filling) of the cardiac cycle;

FIG. 3 is an anatomic superior view of a section of the human heartshown in FIG. 2, with the tricuspid and mitral valves closed and theaortic and pulmonary valves opened during ventricular systole(ventricular emptying) of the cardiac cycle;

FIG. 4 is an anatomic anterior perspective view of the left and rightatria, with portions broken away and in section to show the interior ofthe heart chambers and associated structures, such as the fossa ovalis,coronary sinus, and the great cardiac vein;

FIGS. 5A-5H are sectional views through an isolated aortic annulusshowing a portion of the adjacent left ventricle and aorta, andillustrating a number of steps in deployment of an exemplary prostheticheart valve system of the present invention;

FIG. 5A shows a deflated balloon catheter having a base stent thereonadvanced into position at the aortic annulus;

FIG. 5B shows the balloon on the catheter inflated to expand and deploythe base stent against the aortic annulus;

FIG. 5C shows the deployed base stent in position within the aorticannulus;

FIG. 5D shows a valve component mounted on a balloon catheter advancinginto position within the base stent;

FIG. 5E shows the valve component in a desired implant position at theaortic annulus and within the base stent, with the balloon catheteradvanced farther to displace a nose cone out of engagement with acoupling stent;

FIG. 5F shows the balloon on the catheter inflated to expand and deploya valve component coupling stent against the base stent;

FIG. 5G shows the deflated balloon on the catheter along with the nosecone being removed from within the valve component;

FIG. 5H shows the fully deployed prosthetic heart valve of the presentinvention;

FIG. 6 is an exploded view of an exemplary system for delivering theprosthetic heart valve of the present invention;

FIG. 7 is an assembled view of the delivery system of FIG. 6 showing anose cone extending over a distal end of a valve component couplingstent;

FIG. 8 is a view like FIG. 7 but with a balloon catheter displaceddistally to disengage the nose cone from the coupling stent;

FIG. 9 is an assembled view of the delivery system similar to that shownin FIG. 7 and showing a balloon inflated to expand the valve componentcoupling stent;

FIG. 10 is an exploded elevational view of several components of theintroducing system of FIG. 9, without the balloon catheter, valvecomponent and holder;

FIGS. 11A and 11B are perspective views of an exemplary valve componentassembled on a valve holder of the present invention;

FIG. 11C is a side elevational view of the assembly of FIGS. 11A and11B;

FIGS. 11D and 11E are top and bottom plan views of the assembly of FIGS.11A and 11B;

FIGS. 12A-12B illustrate an exemplary coupling stent in both a flatconfiguration (12A) and a tubular expanded configuration (12B);

FIGS. 13A-13B illustrate an alternative coupling stent having adiscontinuous upper end in both flat and tubular expandedconfigurations;

FIG. 14-17 are plan views of a still further alternative coupling stent;

FIG. 18A-18B are flat and tubular views of an exemplary base stent withupper position markers and a phantom coupling stent superimposedthereover;

FIG. 19 is a flat view of an alternative base stent with a couplingstent superimposed thereover;

FIG. 20 is a sectional view of a coupling stent within a base stentillustrating one method of interlocking; and

FIG. 21-23 is a perspective view of a device for delivering andexpanding a base stent with mechanical fingers.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention attempts to overcome drawbacks associated withconventional, open-heart surgery, while also adopting some of thetechniques of newer technologies which decrease the duration of thetreatment procedure. The prosthetic heart valves of the presentinvention are primarily intended to be delivered and implanted usingconventional surgical techniques, including the aforementionedopen-heart surgery. There are a number of approaches in such surgeries,all of which result in the formation of a direct access pathway to theparticular heart valve annulus. For clarification, a direct accesspathway is one that permits direct (i.e., naked eye) visualization ofthe heart valve annulus. In addition, it will be recognized thatembodiments of the two-stage prosthetic heart valves described hereinmay also be configured for delivery using percutaneous approaches, andthose minimally-invasive surgical approaches that require remoteimplantation of the valve using indirect visualization.

One primary aspect of the present invention is a two-stage prostheticheart valve wherein the tasks of implanting a tissue anchor first andthen a valve member are distinct and certain advantages result. Theexemplary two-stage prosthetic heart valve of the present invention hasan expandable base stent secured to tissue in the appropriate locationusing a balloon or other expansion technique. A hybrid valve member thathas non-expandable and expandable portions then couples to the basestent in a separate or sequential operation. By utilizing an expandablebase stent, the duration of the initial anchoring operation is greatlyreduced as compared with a conventional sewing procedure utilizing anarray of sutures. The expandable base stent may simply be radiallyexpanded outward into contact with the implantation site, or may beprovided with additional anchoring means, such as barbs. The operationmay be carried out using a conventional open-heart approach andcardiopulmonary bypass. In one advantageous feature, the time on bypassis greatly reduced due to the relative speed of implanting theexpandable base stent.

For definitional purposes, the term “base stent,” refers to a structuralcomponent of a heart valve that is capable of attaching to tissue of aheart valve annulus. The base stents described herein are most typicallytubular stents, or stents having varying shapes or diameters. A stent isnormally formed of a biocompatible metal wire frame, such as stainlesssteel or Nitinol. Other base stents that could be used with valves ofthe present invention include rigid rings, spirally-wound tubes, andother such tubes that fit tightly within a valve annulus and define anorifice therethrough for the passage of blood, or within which a valvemember is mounted. It is entirely conceivable, however, that the basestent could be separate clamps or hooks that do not define a continuousperiphery. Although such devices sacrifice some dynamic stability, andspeed and ease of deployment, these devices could be configured to workin conjunction with a particular valve member.

A distinction between self-expanding and balloon-expanding stents existsin the field. A self-expanding stent may be crimped or otherwisecompressed into a small tube and possesses sufficient elasticity tospring outward by itself when a restraint such as an outer sheath isremoved. In contrast, a balloon-expanding stent is made of a materialthat is substantially less elastic, and indeed must be plasticallyexpanded from the inside out when converting from a compressed diameterto an expanded. It should be understood that the term balloon-expandingstents encompasses plastically-expandable stents, whether or not aballoon is used to actually expand it. The material of the stentplastically deforms after application of a deformation force such as aninflating balloon or expanding mechanical fingers. Both alternativeswill be described below. Consequently, the term “balloon-expandablestent” should be considered to refer to the material or type of thestent as opposed to the specific expansion means.

The term “valve member” refers to that component of a heart valve thatpossesses the fluid occluding surfaces to prevent blood flow in onedirection while permitting it in another. As mentioned above, variousconstructions of valve members are available, including those withflexible leaflets and those with rigid leaflets or a ball and cagearrangement. The leaflets may be bioprosthetic, synthetic, or metallic.

A primary focus of the present invention is a two-stage prosthetic heartvalve having a first stage in which a base stent secures to a valveannulus, and a subsequent second stage in which a valve member connectsto the base stent. It should be noted that these stages can be donealmost simultaneously, such as if the two components were mounted on thesame delivery device, or can be done in two separate clinical steps,with the base stent deployed using a first delivery device, and then thevalve member using another delivery device. It should also be noted thatthe term “two-stage” refers to the two primary steps of anchoringstructure to the annulus and then connecting a valve member, which doesnot necessarily limit the valve to just two parts.

Another potential benefit of a two-stage prosthetic heart valve,including a base stent and a valve member, is that the valve member maybe replaced after implantation without replacing the base stent. Thatis, an easily detachable means for coupling the valve member and basestent may be used that permits a new valve member to be implanted withrelative ease. Various configurations for coupling the valve member andbase stent are described herein.

It should be understood, therefore, that certain benefits of theinvention are independent of whether the base stent is expandable ornot. That is, various embodiments illustrate an expandable base stentcoupled to a hybrid valve member that has non-expandable and expandableportions. However, the same coupling structure may be utilized for anon-expandable base stent and hybrid valve member. Therefore, theinvention should be interpreted via the appended claims.

As a point of further definition, the term “expandable” is used hereinto refer to a component of the heart valve capable of expanding from afirst, delivery diameter to a second, implantation diameter. Anexpandable structure, therefore, does not mean one that might undergoslight expansion from a rise in temperature, or other such incidentalcause. Conversely, “non-expandable” should not be interpreted to meancompletely rigid or a dimensionally stable, as some slight expansion ofconventional “non-expandable” heart valves, for example, may beobserved.

In the description that follows, the term “body channel” is used todefine a blood conduit or vessel within the body. Of course, theparticular application of the prosthetic heart valve determines the bodychannel at issue. An aortic valve replacement, for example, would beimplanted in, or adjacent to, the aortic annulus. Likewise, a mitralvalve replacement will be implanted at the mitral annulus. Certainfeatures of the present invention are particularly advantageous for oneimplantation site or the other. However, unless the combination isstructurally impossible, or excluded by claim language, any of the heartvalve embodiments described herein could be implanted in any bodychannel.

FIGS. 5A-5H are sectional views through an isolated aortic annulus AAshowing a portion of the adjacent left ventricle LV and ascending aortawith sinus cavities S. The two coronary sinuses CS are also shown. Theseries of views show snapshots of a number of steps in deployment of anexemplary prosthetic heart valve system of the present invention, whichcomprises a two-component system. A first component is a base stent thatis deployed against the native leaflets or, if the leaflets are excised,against the debrided aortic annulus AA. A second valve component fitswithin the base stent and anchors thereto. Although two-part valves areknown in the art, this is believed to be the first that utilizes a stentwithin a stent in conjunction with a non-expandable valve.

FIG. 5A shows a catheter 20 having a balloon 22 in a deflated state neara distal end with a tubular base stent 24 crimped thereover. The stent24 is shown in a radially constricted, undeployed configuration. Thecatheter 20 has been advanced to position the base stent 24 so that itis approximately axially centered at the aortic annulus AA.

FIG. 5B shows the balloon 22 on the catheter 20 inflated to expand anddeploy the base stent 24 against the aortic annulus AA, and FIG. 5Cshows the deployed base stent in position after deflation of the balloon22 and removal of the catheter 20. The stent 24 provides a base withinand against a body lumen (e.g., a valve annulus). Although a stent isdescribed for purposes of illustration, any member capable of anchoringwithin and against the body lumen and then coupling to the valvecomponent may be used. In a preferred embodiment, the base stent 24comprises a plastically-expandable cloth-covered stainless-steel tubularstent. One advantage of using a plastically-expandable stent is theability to expand the native annulus to receive a larger valve size thanwould otherwise be possible with conventional surgery. Desirably, theleft ventricular outflow tract (LVOT) is significantly expanded by atleast 10%, or for example by 1.5-5 mm, and the surgeon can select avalve component 30 with a larger orifice diameter relative to anunexpanded annulus. On the other hand, the present invention could alsouse a self-expanding base stent 24 which is then reinforced by thesubsequently implanted valve component 30. Because the valve component30 has a non-compressible part, the prosthetic valve 34, and desirably aplastically-expandable coupling stent 36, it effectively resists recoilof the self-expanded base stent 24.

With continued reference to FIG. 5B, the stent 24 has a diameter sizedto be deployed at the location of the native valve (e.g., along theaortic annulus). A portion of the stent 24 may expand outwardly into therespective cavity adjacent the native valve. For example, in an aorticvalve replacement, an upper portion may expand into the area of thesinus cavities just downstream from the aortic annulus. Of course, careshould be taken to orient the stent 24 so as not to block the coronaryopenings. The stent body is preferably configured with sufficient radialstrength for pushing aside the native leaflets and holding the nativeleaflets open in a dilated condition. The native leaflets provide astable base for holding the stent, thereby helping to securely anchorthe stent in the body. To further secure the stent to the surroundingtissue, the lower portion may be configured with anchoring members, suchas, for example, hooks or barbs (not shown).

As will be described in more detail below, the prosthetic valve systemincludes a valve component that may be quickly and easily connected tothe stent 24. It should be noted here that the base stents describedherein can be a variety of designs, including having thediamond/chevron-shaped openings shown or other configurations. Thematerial depends on the mode of delivery (i.e., balloon- orself-expanding), and the stent can be bare strut material or covered topromote ingrowth and/or to reduce paravalvular leakage. For example, asuitable cover that is often used is a sleeve of fabric such as Dacron.

One primary advantage of the prosthetic heart valve system of thepresent invention is the speed of deployment. Therefore, the base stent24 may take a number of different configurations as long as it does notrequire the time-consuming process of suturing it to the annulus. Forinstance, another possible configuration for the base stent 24 is onethat is not fully expandable like the tubular stent as shown. That is,the base stent 24 may have a non-expandable ring-shaped orifice fromwhich an expandable skirt stent or series of anchoring barbs deploy.

FIG. 5D shows a valve component 30 mounted on a balloon catheter 32advancing into position within the base stent 24. The valve component 30comprises a prosthetic valve 34 and a coupling stent 36 attached to andprojecting from a distal end thereof. In its radially constricted orundeployed state, the coupling stent 36 assumes a conical inward taperin the distal direction. The catheter 32 extends through the valvecomponent 30 and terminates in a distal nose cone 38 which has a conicalor bell-shape and covers the tapered distal end of the coupling stent36. Although not shown, the catheter 32 extends through an introducingcannula and valve holder.

When used for aortic valve replacement, the prosthetic valve 34preferably has three flexible leaflets which provide the fluid occludingsurfaces to replace the function of the native valve leaflets. Invarious preferred embodiments, the valve leaflets may be taken fromanother human heart (cadaver), a cow (bovine), a pig (porcine valve) ora horse (equine). In other preferred variations, the valve member maycomprise mechanical components rather than biological tissue. The threeleaflets are supported by three commissural posts. A ring is providedalong the base portion of the valve member.

In a preferred embodiment, the prosthetic valve 34 partly comprises acommercially available, non-expandable prosthetic heart valve, such asthe Carpentier-Edwards PERIMOUNT Magna® Aortic Heart Valve availablefrom Edwards Lifesciences of Irvine, Calif. In this sense, a“commercially available” prosthetic heart valve is an off-the-shelf(i.e., suitable for stand-alone sale and use) prosthetic heart valvedefining therein a non-expandable, non-collapsible orifice and having asewing ring capable of being implanted using sutures through the sewingring in an open-heart, surgical procedure. The particular approach intothe heart used may differ, but in surgical procedures the heart isstopped and opened, in contrast to beating heart procedures where theheart remains functional. To reiterate, the terms “non-expandable” and“non-collapsible” should not be interpreted to mean completely rigid anddimensionally stable, merely that the valve is notexpandable/collapsible like some proposed minimally-invasively orpercutaneously-delivered valves.

An implant procedure therefore involves first delivering and expandingthe base stent 24 at the aortic annulus, and then coupling the valvecomponent 30 including the valve 34 thereto. Because the valve 34 isnon-expandable, the entire procedure is typically done using theconventional open-heart technique. However, because the base stent 24 isdelivered and implanted by simple expansion, and then the valvecomponent 30 attached thereto by expansion, both without suturing, theentire operation takes less time. This hybrid approach will also be muchmore comfortable to surgeons familiar with the open-heart procedures andcommercially available heart valves.

Moreover, the relatively small change in procedure coupled with the useof proven heart valves should create a much easier regulatory path thanstrictly expandable, remote procedures. Even if the system must bevalidated through clinical testing to satisfy the Pre-Market Approval(PMA) process with the FDA (as opposed to a 510 k submission), theacceptance of the valve component 30 at least will be greatlystreamlined with a commercial heart valve that is already approved, suchas the Magna® Aortic Heart Valve.

The prosthetic valve 34 is provided with an expandable couplingmechanism in the form of the coupling stent 36 for securing the valve tothe base stent 24. Although the coupling stent 36 is shown, the couplingmechanism may take a variety of different forms, but eliminates the needfor connecting sutures and provides a rapid connection means.

In FIG. 5E the valve component 30 has advanced to a desired implantposition at the aortic annulus AA and within the base stent 24. Theprosthetic valve 34 may include a suture-permeable ring 42 thatdesirably abuts the aortic annulus AA. More preferably, the sewing ring42 is positioned supra-annularly, or above the narrowest point of theaortic annulus AA, so as to allow selection of a larger orifice sizethan a valve placed intra-annularly. With the aforementioned annulusexpansion using the base stent 24, and the supra-annular placement, thesurgeon may select a valve having a size one or two increments largerthan previously conceivable. As mentioned, the prosthetic valve 34 isdesirably a commercially available heart valve having a sewing ring 42.The balloon catheter 32 has advanced relative to the valve component 30to displace the nose cone 38 out of engagement with the coupling stent36. A dilatation balloon 40 on the catheter 30 can be seen just beyondthe distal end of the coupling stent 36.

FIG. 5F shows the balloon 40 on the catheter 32 inflated to expand anddeploy the coupling stent 36 against the base stent 24. The balloon 40is desirably inflated using controlled, pressurized, sterile physiologicsaline. The coupling stent 36 transitions between its conical contractedstate and its generally tubular expanded state. Simple interferencebetween the coupling stent 36 and the base stent 24 may be sufficient toanchor the valve component 30 within the base stent, or interactingfeatures such as projections, hooks, barbs, fabric, etc. may beutilized.

Because the base stent 24 expands before the valve component 30 attachesthereto, a higher strength stent (self- or balloon-expandable)configuration may be used. For instance, a relatively robust base stent24 may be used to push the native leaflets aside, and the absent valvecomponent 30 is not damaged or otherwise adversely affected during thehigh-pressure base stent deployment. After the base stent 24 deploys inthe body channel, the valve component 30 connects thereto by deployingthe coupling stent 36, which may be somewhat more lightweight requiringsmaller expansion forces. Also, the balloon 40 may have a larger distalexpanded end than its proximal expanded end so as to apply more force tothe coupling stent 36 than to the prosthetic valve 34. In this way, theprosthetic valve 34 and flexible leaflets therein are not subject tohigh expansion forces from the balloon 40. Indeed, although balloondeployment is shown, the coupling stent 36 may also be a self-expandingtype of stent. In the latter configuration, the nose cone 38 is adaptedto retain the coupling stent 36 in its constricted state prior toposition in the valve component 30 within the base stent 24.

As noted above, the base stents described herein could include barbs orother tissue anchors to further secure the stent to the tissue, or tosecure the coupling stent 36 to the base stent 24. Further, the barbscould be deployable (e.g., configured to extend or be pushed radiallyoutward) by the expansion of a balloon. Preferably, the coupling stent36 is covered to promote in-growth and/or to reduce paravalvularleakage, such as with a Dacron tube or the like.

FIG. 5G shows the deflated balloon 40 on the catheter 32 along with thenose cone 38 being removed from within the valve component 30. Finally,FIG. 5H shows the fully deployed prosthetic heart valve system of thepresent invention including the valve component 30 coupled to the basestent 24 within the aortic annulus AA.

FIG. 6 is an exploded view, and FIGS. 7 and 8 are assembled views, of anexemplary system 50 for delivering the prosthetic heart valve of thepresent invention. Modified components of the delivery system 50 arealso shown in FIGS. 9 and 10. The delivery system 50 includes a ballooncatheter 52 having the balloon 40 on its distal end and an obturator 54on a proximal end. The obturator 54 presents a proximal coupling 56 thatreceives a luer connector or other such fastener of a Y-fitting 58. Theaforementioned nose cone 38 may attach to the distalmost end of thecatheter 52, but more preferably attaches to a wire (not shown) insertedthrough the center lumen of the balloon catheter 52.

The catheter 52 and the nose cone 38 pass through a hollow handle 60having a proximal section 62 and a distal section 64. A distal end ofthe distal handle section 64 firmly attaches to a hub 66 of a valveholder 68, which in turn attaches to the prosthetic heart valvecomponent 30. Details of the valve holder 68 will be given below withreference to FIGS. 11A-11E.

The two sections 62, 64 of the handle 60 are desirably formed of a rigidmaterial, such as a molded plastic, and coupled to one another to form arelatively rigid and elongated tube for manipulating the prostheticvalve component 30 attached to its distal end. In particular, the distalsection 64 may be easily coupled to the holder hub 66 and thereforeprovide a convenient tool for managing the valve component 30 duringpre-surgical rinsing steps. For this purpose, the distal section 64features a distal tubular segment 70 that couples to the holder hub 66,and an enlarged proximal segment 72 having an opening on its proximalend that receives a tubular extension 74 of the proximal handle section62. FIG. 6 shows an O-ring 76 that may be provided on the exterior ofthe tubular extension 74 for a frictional interference fit to preventthe two sections from disengaging. Although not shown, the distaltubular segment 70 may also have an O-ring for firmly coupling to theholder hub 66, or may be attached with threading or the like. In onepreferred embodiment, the balloon 40 on the catheter 52 is packagedwithin the proximal handle section 62 for protection and ease ofhandling. Coupling the proximal and distal handle sections 62, 64therefore “loads” the system 50 such that the balloon catheter 52 may beadvanced through the continuous lumen leading to the valve component 30.

FIGS. 9 and 10 illustrate a delivery system 50 similar to that shown inFIG. 7, but with alternative couplers 77 on both the proximal and distalhandle sections 62, 64 in the form of cantilevered teeth that snap intocomplementary recesses formed in the respective receiving apertures.Likewise, threading on the mating parts could also be used, as well asother similar expedients. FIG. 9 shows the balloon 40 inflated to expandthe valve component coupling stent 36.

In a preferred embodiment, the prosthetic valve component 30incorporates bioprosthetic tissue leaflets and is packaged and storedattached to the holder 68 but separate from the other introductionsystem 50 components. Typically, bioprosthetic tissue is packaged andstored in a jar with preservative solution for long shelf life, whilethe other components are packaged and stored dry.

When assembled as seen in FIGS. 7-9, an elongated lumen (not numbered)extends from the proximal end of the Y-fitting 58 to the interior of theballoon 40. The Y-fitting 58 desirably includes an internally threadedconnector 80 for attachment to an insufflation system, or a side port 82having a luer fitting 84 or similar expedient may be used forinsufflation of the balloon 40.

FIGS. 7 and 8 show two longitudinal positions of the catheter 52 andassociated structures relative to the handle 60 and its associatedstructures. In a retracted position shown in FIG. 7, the balloon 40primarily resides within the distal handle section 64. FIG. 7illustrates the delivery configuration of the introduction system 50, inwhich the surgeon advances the prosthetic valve component 30 fromoutside the body into a location adjacent the target annulus. The nosecone 38 extends around and protects a distal end of the conicalundeployed coupling stent 36. This configuration is also seen in FIG.5D, albeit with the holder 68 removed for clarity. Note the spacing Sbetween the proximal coupling 56 and the proximal end of the handle 60.

As explained above with respect to FIGS. 5A-5H, the surgeon advances theprosthetic valve component 30 into its desired implantation position atthe valve annulus, and then advances the balloon 40 through the valvecomponent and inflates it. To do so, the operator converts the deliverysystem 50 from the retracted configuration of FIG. 7 to the deploymentconfiguration of FIG. 8, with the balloon catheter 40 displaced distallyas indicated by the arrow 78 to disengage the nose cone 38 from thecoupling stent 36. Note that the proximal coupling 56 now contacts theproximal end of the handle 60, eliminating the space S indicated in FIG.7.

It should be understood that the prosthetic valve component 30 may beimplanted at the valve annulus with a pre-deployed base stent 24, asexplained above, or without. The coupling stent 36 may be robust enoughto anchor the valve component 30 directly against the native annulus(with or without leaflet excision) in the absence of the base stent 24.Consequently, the description of the system 50 for introducing theprosthetic heart valve should be understood in the context of operatingwith or without the pre-deployed base stent 24.

Prior to a further description of operation of the delivery system 50, amore detailed explanation of the valve component 30 and valve holder 68is necessary. FIGS. 11A-11E show a number of perspective and other viewsof the exemplary valve component 30 mounted on the delivery holder 68 ofthe present invention. As mentioned, the valve component 30 comprisesthe prosthetic valve 34 having the coupling stent 36 attached to aninflow end thereof. In a preferred embodiment, the prosthetic valve 34comprises a commercially available off-the-shelf non-expandable,non-collapsible commercial prosthetic valve. Any number of prostheticheart valves can be retrofit to attach the coupling stent 36, and thusbe suitable for use in the context of the present invention. Forexample, the prosthetic valve 34 may be a mechanical valve or a valvewith flexible leaflets, either synthetic or bioprosthetic. In apreferred embodiment, however, the prosthetic valve 34 includesbioprosthetic tissue leaflets 86 (FIG. 11A). Furthermore, as mentionedabove, the prosthetic valve 34 is desirably a Carpentier-EdwardsPERIMOUNT Magna® Aortic Heart Valve (e.g., model 3000TFX) available fromEdwards Lifesciences of Irvine, Calif.

The coupling stent 36 preferably attaches to the ventricular (or inflow)aspect of the valve's sewing ring 42 during the manufacturing process ina way that preserves the integrity of the sewing ring and preventsreduction of the valve's effective orifice area (EOA). Desirably, thecoupling stent 36 will be continuously sutured to sewing ring 42 in amanner that maintains the outer contours of the sewing ring. Sutures maybe passed through apertures or eyelets in the stent skeleton, or througha cloth covering that in turn is sewn to the skeleton. Other connectionsolutions include prongs or hooks extending inward from the stent, ties,Velcro, snaps, adhesives, etc. Alternatively, the coupling stent 36 maybe more rigidly connected to rigid components within the prostheticvalve 34. During implant, therefore, the surgeon can seat the sewingring 42 against the annulus in accordance with a conventional surgery.This gives the surgeon familiar tactile feedback to ensure that theproper patient-prosthesis match has been achieved. Moreover, placementof the sewing ring 42 against the outflow side of the annulus helpsreduce the probability of migration of the valve component 30 toward theventricle.

The coupling stent 36 may be a pre-crimped, tapered, 316L stainlesssteel balloon-expandable stent, desirably covered by a polyester skirt88 to help seal against paravalvular leakage and promote tissue ingrowthonce implanted within the base stent 24 (see FIG. 5F). The couplingstent 36 transitions between the tapered constricted shape of FIGS.11A-11E to its flared expanded shape shown in FIG. 5F, and also in FIG.10.

The coupling stent 36 desirably comprises a plurality of sawtooth-shapedor otherwise angled, serpentine or web-like struts 90 connected to threegenerally axially-extending posts 92. As will be seen below, the posts92 desirably feature a series of evenly spaced apertures to whichsutures holding the polyester skirt 88 in place may be anchored. As seenbest in FIG. 5F, the stent 36 when expanded flares outward and conformsclosely against the inner surface of the base stent 24, and has an axiallength substantially the same as the base stent. Anchoring devices suchas barbs or other protuberances from the coupling stent 36 may beprovided to enhance the frictional hold between the coupling stent andthe base stent 24.

It should be understood that the particular configuration of thecoupling stent, whether possessing straight or curvilinear struts 90,may be modified as needed. There are numerous stent designs, asdescribed below with reference to FIGS. 12-17, any of which potentiallymay be suitable. Likewise, although the preferred embodimentincorporates a balloon-expandable coupling stent 36, a self-expandingstent could be substituted with certain modifications, primarily to thedelivery system. The same flexibility and design of course applies tothe base stent 24. In a preferred embodiment, both the base stent 24 andthe coupling stent 36 are desirably plastically-expandable to provide afirmer anchor for the valve 34; first to the annulus with or withoutnative leaflets, and then between the two stents. The stents may beexpanded using a balloon or mechanical expander as described below.

Still with reference to FIGS. 11A-11E, the holder 68 comprises theaforementioned proximal hub 66 and a thinner distal extension 94 thereofforming a central portion of the holder. Three legs 96 a, 96 b, 96 ccircumferentially equidistantly spaced around the central extension 94and projecting radially outward therefrom comprise inner struts 98 andouter commissure rests 100. The prosthetic valve 34 preferably includesa plurality, typically three, commissures 102 that project in an outflowdirection. Although not shown, the commissure rests 100 preferablyincorporate depressions into which fit the tips of the commissures 102.

In one embodiment, the holder 68 is formed of a rigid polymer such asDelrin or polypropylene that is transparent to increase visibility of animplant procedure. As best seen in FIG. 11E, the holder 68 exhibitsopenings between the legs 96 a, 96 b, 96 c to provide a surgeon goodvisibility of the valve leaflets 86, and the transparency of the legsfurther facilitates visibility and permits transmission of lighttherethrough to minimize shadows. Although not described in detailherein, FIG. 11E also illustrate a series of through holes in the legs96 a, 96 b, 96 c permitting connecting sutures to be passed throughfabric in the prosthetic valve 34 and across a cutting guide in eachleg. As is known in the art, severing a middle length of suture that isconnected to the holder 68 and passes through the valve permits theholder to be pulled free from the valve when desired.

FIGS. 11C and 11D illustrate a somewhat modified coupling stent 36 fromthat shown in FIGS. 11A and 11B, wherein the struts 90 andaxially-extending posts 92 are better defined. Specifically, the posts92 are somewhat wider and more robust than the struts 90, as the latterprovide the stent 36 with the ability to expand from the conical shapeshown to a more tubular configuration. Also, a generally circularreinforcing ring 104 abuts the valve sewing ring 42. Both the posts 92and the ring 104 further include a series of through holes 106 that maybe used to secure the polyester skirt 88 to the stent 36 using suturesor the like. A number of variants of the coupling stent 36 are alsodescribed below.

FIGS. 12A-12B illustrate the exemplary coupling stent 36 in both a flatconfiguration (12A) and a tubular configuration (12B) that is generallythe expanded shape. As mentioned, the web-like struts 90 and areinforcing ring 104 connect three generally axially-extending posts 92.A plurality of evenly spaced apertures 106 provide anchors for holdingthe polyester skirt 88 (see FIG. 11B) in place. In the illustratedembodiment, the web-like struts 90 also include a series ofaxially-extending struts 108. An upper end of the coupling stent 36 thatconnects to the sewing ring of the valve and is defined by thereinforcing ring 104 follows an undulating path with alternating arcuatetroughs 110 and peaks 112. As seen from FIG. 11C, the exemplaryprosthetic valve 34 has an undulating sewing ring 42 to which the upperend of the coupling stent 36 conforms. In a preferred embodiment, thegeometry of the stent 36 matches that of the undulating sewing ring 42.Of course, if the sewing ring of the prosthetic valve is planar, thenthe upper end of the coupling stent 36 will also be planar. It should benoted also that the tubular version of FIG. 12B is an illustration of anexpanded configuration, although the balloon 40 may over-expand the free(lower) end of the stent 36 such that it ends up being slightly conical.

FIGS. 13A and 13B show an alternative coupling stent 120, again inflattened and tubular configurations, respectively. As with the firstembodiment, the coupling stent 120 includes web-like struts 122extending between a series of axially-extending struts 124. In thisembodiment, all of the axially-extending struts 124 are substantiallythe same thin cross-sectional size. The upper or connected end of thestent 120 again includes a reinforcing ring 126, although this versionis interrupted with a series of short lengths separated by gaps. Theupper end defines a plurality of alternating troughs 128 and peaks 130,with lengths of the reinforcing ring 126 defining the peaks. Theaxially-extending struts 124 are in-phase with the scalloped shape ofthe upper end of the stent 120, and coincide with the peaks and themiddle of the troughs.

The gaps between the lengths making up the reinforcing ring 126 permitthe stent 120 to be matched with a number of different sized prostheticvalves 34. That is, the majority of the stent 120 is expandable having avariable diameter, and providing gaps in the reinforcing ring 126 allowsthe upper end to also have a variable diameter so that it can be shapedto match the size of the corresponding sewing ring. This reducesmanufacturing costs as correspondingly sized stents need not be used foreach different sized valve.

FIG. 14 is a plan view of a still further alternative coupling stent 132that is very similar to the coupling stent 120, including web-likestruts 134 connected between a series of axially-extending struts 136,and the upper end is defined by a reinforcing ring 138 formed by aseries of short lengths of struts. In contrast to the embodiment ofFIGS. 13A and 13B, the peaks of the undulating upper end have gaps asopposed to struts. Another way to express this is that theaxially-extending struts 136 are out-of-phase with the scalloped shapeof the upper end of the stent 132, and do not correspond to the peaksand the middle of the troughs.

FIG. 15 illustrates an exemplary coupling stent 140 again having theexpandable struts 142 between the axially-extending struts 144, and anupper reinforcing ring 146. The axially-extending struts 144 arein-phase with peaks and troughs of the upper end of the stent. Thereinforcing ring 146 is a cross between the earlier-described such ringsas it is continuous around its periphery but also has a variablediameter. That is, the ring 146 comprises a series of lengths of struts148 of fixed length connected by thinner bridge portions 150 of variablelength. The bridge portions 150 are each formed with a radius so thatthey can be either straightened (lengthened) or bent more (compressed).A series of apertures 152 are also formed in an upper end of the stent142 provide anchor points for sutures or other attachment means whensecuring the stent to the sewing ring of the corresponding prostheticvalve.

In FIG. 16, an alternative coupling stent 154 is identical to the stent140 of FIG. 15, although the axially-extending struts 156 areout-of-phase with the peaks and troughs of the undulating upper end.

FIG. 17 shows a still further variation on a coupling stent 160, whichhas a series of expandable struts 162 connecting axially-extendingstruts 164. As with the version shown in FIGS. 12A and 12B, the web-likestruts 162 also include a series of axially-extending struts 166,although these are thinner than the main axial struts 164. A reinforcingring 168 is also thicker than the web-like struts 162, and features oneor more gaps 170 in each trough such that the ring is discontinuous andexpandable. Barbs 172, 174 on the axially extending struts 164, 166 maybe utilized to enhance retention between the coupling stent 160 and abase stent with which it cooperates, or with annular tissue insituations where there is no base stent, as explained above.

As mentioned above, the two-component valve systems described hereinutilize an outer or base stent (such as base stent 24) and a valvecomponent having an inner or valve stent (such as coupling stent 36).The valve and its stent advance into the lumen of the pre-anchored outerstent and the valve stent expands to join the two stents and anchor thevalve into its implant position. It is important that the inner stentand outer stent be correctly positioned both circumferentially andaxially to minimize subsequent relative motion between the stents.Indeed, for the primary application of an aortic valve replacement, thecircumferential position of the commissures of the valve relative to thenative commissures is very important. A number of variations of couplingstent that attach to the valve component have been shown and describedabove. FIGS. 18-20 illustrate exemplary base stents and cooperationbetween the two stents.

FIGS. 18A and 18B show an exemplary embodiment of a base stent 180comprising a plurality of radially-expandable struts 182 extendingbetween a plurality of generally axially-extending struts 184. In theillustrated embodiment the struts 182 form chevron patterns between thestruts 184, although other configurations such as serpentine ordiamond-shaped could also be used. The top and bottom rows of theradially-expandable struts 182 are arranged in apposition so as to forma plurality of triangular peaks 186 and troughs 188. The axial struts184 are in-phase with the troughs 188.

The flattened view of FIG. 18A shows four axial projections 190 thateach extend upward from one of the axial struts 184. Although fourprojections 190 are shown, the exemplary base stent 180 desirably hasthree evenly circumferentially spaced projections, as seen around theperiphery in the tubular version of FIG. 18B, providing location markersfor the base stent. These markers thus make it easier for the surgeon toorient the stent 180 such that the markers align with the nativecommissures. Furthermore, as the valve component advances to within thebase stent 180, the visible projections 190 provide reference marks suchthat the inner stent can be properly oriented within the base stent. Inthis regard the projections 190 may be differently colored than the restof the stent 180, or have radiopaque indicators thereon.

The length of the projections 190 above the upper row of middle struts182 may also be calibrated to help the surgeon axially position thestent 180. For example, the distance from the tips of the projections190 to the level of the native annulus could be determined, and theprojections 190 located at a particular anatomical landmark such as justbelow the level of the coronary ostia.

An undulating dashed line 192 in FIG. 18A represents the upper end ofthe inner or coupling stent 140, which is shown in phantom superimposedover the base stent 180. As such, the dashed line 192 also represents anundulating sewing ring, and it bears repeating that the sewing ringcould be planar such that the upper end of the coupling stent is alsoplanar. The coupling stent 140 includes axially-extending struts thatare in-phase with the respective peaks and troughs of the scallopedupper end of the stent. In the illustrated combination, the peaks of thescalloped upper end of the coupling stent (dashed line 192) correspondrotationally (are in-phase) with the axial struts 184 that have theprojections 190. Therefore, because the coupling stent 140 axial strutsare in-phase with the peaks of the upper end thereof, they are alsoin-phase with the axial struts 184 of the base stent 180. Conversely, acoupling stent may have axial struts out-of-phase with peaks of theupper end thereof, in which case the respective axial struts of the twostents are also out-of-phase.

FIG. 19 shows an alternative base stent 200 that generally has the samecomponents as the base stent 180 of FIG. 18A, but the axial struts 184extend between the peaks 186 of the outer rows of middle struts 182. Inthe earlier embodiment, the axial struts 184 extended between thetroughs 188. The coupling stent 154 of FIG. 16 is shown in phantomsuperimposed over the base stent 200 to illustrate how the axial strutsof the two stents are now out-of-phase to increase interlockingtherebetween.

The stent 200 also exhibits different rows of middle struts 182.Specifically, a first row 202 a defines V's having relatively shallowangles, a second row 202 b defines V's with medium angles, and a thirdrow 202 c defined V's with more acute angles. The different anglesformed by the middle struts 182 in these rows helps shape the stent intoa conical form when expanded. There is, the struts in the third row 202c which is farthest from the prosthetic valve have the greatest capacityfor expansion to accommodate the transition from the collapsed conicalshape of the stent to the expanded tubular shape.

Those of skill in the art will understand that there are many ways toincrease retention between the two stents. For example, the peaks andtroughs of the web-like expandable struts on the two stents could beoriented out-of-phase or in-phase. In a preferred embodiment the peaksand troughs of the two stents are out of phase so that expansion of theinner stent causes its peaks to deform outwardly into the troughs of theouter stent, and thereby provide interlocking structure therebetween.The variations described above provide a number of permutations of thiscooperation.

Additionally, axial projections on one or both of stents could be bentto provide an interference with the other stent. For example, the lowerends of the axial struts 108 in the stent 36 shown in FIG. 12A could bebent outward by expansion of a non-uniform shaped balloon such that theyextend in voids within the outer stent. Likewise, the embodiment of FIG.17 illustrates barbs 172, 174 that can be bent outward into interferencewith the corresponding base stent. Strut ends or barbs that transitionfrom one position to another to increase retention between the twostents can be actuated by mechanical bending, such as with a balloon, orthrough an automatic shape change upon installation within the body.Namely, some shape memory alloys such as Nitinol can be designed toundergo a shape change upon a temperature change, such that they assumea first shape at room temperature, and a second shape at bodytemperature.

FIG. 20 illustrates a simplified means for increasing retention betweenthe two stents. An inner valve stent 210 fits within an outer base stent212 such that a lower end 214 thereof extends below the outer stent. Byover-expansion of the balloon within the inner stent 210, the lower end214 is caused to bend or wrap outward to prevent relative upwardmovement of the inner stent within the outer stent.

FIG. 21 is a perspective view of a device 220 for delivering andexpanding a base stent 222 with a mechanical expander 224. In theillustrated embodiment, the expander 224 includes a plurality ofspreadable fingers 226 over which the base stent 22 is crimped. Thedevice 220 includes a syringe-like apparatus including a barrel 230within which a plunger 232 linearly slides. The fingers 226 are axiallyfixed but capable of pivoting or flexing with respect to the barrel 230.The distal end of the plunger 232 has an outer diameter that is greaterthan the diameter circumscribed by the inner surfaces of the spreadablefingers 226. Preferably there is a proximal lead-in ramp on the insideof the fingers 226 such that distal movement of the plunger 232 withrespect to the barrel 230 gradually cams the fingers outward. The twopositions of the plunger 232 are shown in FIGS. 21 and 23.

As an alternative to simple linear movement of the plunger 232, it mayalso be threadingly received within the barrel 230. Still further, theplunger 232 may be formed in two parts freely rotatable with respect toone another, with a proximal part threadingly received within the barrel230 while a distal part does not rotate with respect to the barrel andmerely cams the fingers 226 outward. Still further, a mechanical linkagemay be used instead of a camming action whereby levers hinged togethercreate outward movement of the fingers 226. And even further still, ahybrid version using an inflatable balloon with mechanical parts mountedon the outside of the balloon may be utilized. Those of skill in the artwill understand that numerous variants on this mechanism are possible,the point being that balloon expansion is not only vehicle.

Desirably, the fingers 226 have a contoured exterior profile such thatthey expand the base stent 222 into a particular shape that better fitsthe heart valve annulus. For instance, the base stent 222 may beexpanded into an hourglass shape with wider upper and lower ends and asmaller midsection, and/or an upper end may be formed with a tri-lobularshape to better fit the aortic sinuses. In the latter case, thetri-lobular shape is useful for orienting the base stent 222 uponimplant, and also for orienting the coupling stent of the valvecomponent that is received therewithin.

In another advantageous feature, the two-component valve systemillustrated in the preceding figures provides a device and method thatsubstantially reduces the time of the surgical procedure as comparedwith replacement valves that are sutured to the tissue after removingthe native leaflets. For example, the stent 24 of FIGS. 5-9 may bedeployed quickly and the valve component 30 may also be quickly attachedto the stent. This reduces the time required on extracorporealcirculation and thereby substantially reduces the risk to the patient.

In addition to speeding up the implant process, the present inventionhaving the pre-anchored stent, within which the valve and its stentmount, permits the annulus to be expanded to accommodate a larger valvethan otherwise would be possible. In particular, clinical research hasshown that the left ventricular outflow tract (LVOT) can besignificantly expanded by a balloon-expandable stent and still retainnormal functioning. In this context, “significantly expanding” the LVOTmeans expanding it by at least 10%, more preferably between about10-30%. In absolute terms, the LVOT may be expanded 1.5-5 mm dependingon the nominal orifice size. This expansion of the annulus creates anopportunity to increase the size of a surgically implanted prostheticvalve. The present invention employs a balloon-expandable base stent,and a balloon-expandable valve stent. The combination of these twostents permits expansion of the LVOT at and just below the aorticannulus, at the inflow end of the prosthetic valve. The interference fitcreated between the outside of the base stent and the LVOT secures thevalve without pledgets or sutures taking up space, thereby allowing forplacement of the maximum possible valve size. A larger valve size thanwould otherwise be available with conventional surgery enhancesvolumetric blood flow and reduces the pressure gradient through thevalve.

It will be appreciated by those skilled in the art that embodiments ofthe present invention provide important new devices and methods whereina valve may be securely anchored to a body lumen in a quick andefficient manner. Embodiments of the present invention provide a meansfor implanting a prosthetic valve in a surgical procedure withoutrequiring the surgeon to suture the valve to the tissue. Accordingly,the surgical procedure time is substantially decreased. Furthermore, inaddition to providing a base stent for the valve, the stent may be usedto maintain the native valve in a dilated condition. As a result, it isnot necessary for the surgeon to remove the native leaflets, therebyfurther reducing the procedure time.

It will also be appreciated that the present invention provides animproved system wherein a valve member may be replaced in a more quickand efficient manner. More particularly, it is not necessary to cut anysutures in order to remove the valve. Rather, the valve member may bedisconnected from the stent (or other base stent) and a new valve membermay be connected in its place. This is an important advantage when usingbiological tissue valves or other valves having limited design lives.

While the invention has been described in its preferred embodiments, itis to be understood that the words which have been used are words ofdescription and not of limitation. Therefore, changes may be made withinthe appended claims without departing from the true scope of theinvention.

1. A prosthetic heart valve system, comprising: a base stent adapted toanchor against a heart valve annulus and defining an orifice therein;and a valve component including a non-expandable, non-collapsibleprosthetic valve, the valve component further including an expandablecoupling stent extending from an inflow end thereof, the coupling stenthaving a contracted state for delivery to an implant position and anexpanded state configured for outward connection to the base stent,wherein the prosthetic valve comprises a sewing ring surrounding aninflow end, and wherein an outflow end of the coupling stent iscontinuously sutured to the sewing ring.
 2. The system of claim 1,wherein the base stent is expandable and has a contracted state fordelivery to an implant position adjacent a heart valve annulus and anexpanded state sized to contact and anchor against the heart valveannulus.
 3. The system of claim 2, wherein the base stent is plasticallyexpandable.
 4. The system of claim 1, wherein the coupling stent isplastically expandable.
 5. The system of claim 1, wherein the contractedstate of the coupling stent is conical, tapering down in a distaldirection.
 6. The system of claim 5, wherein the coupling stentcomprises a plurality of radially expandable struts at least some ofwhich are arranged in rows, and wherein the distalmost row has thegreatest capacity for expansion from the contracted state to theexpanded state.
 7. The system of claim 1, wherein the coupling stentcomprises a plurality of radially expandable struts, and a row farthestfrom the prosthetic valve has alternating peaks and valleys, and whereinthe base stent includes apertures into which the peaks of the couplingstent may project to interlock the two stents.
 8. The system of claim 1,wherein the base stent includes a plurality of radially expandablestruts between axially-oriented struts, and at least some of theaxially-oriented struts have upper projections that demark locationsaround the stent.
 9. The system of claim 1, wherein both the base stentand the coupling stent have a plurality of radially expandable strutsbetween axially-oriented struts, and wherein the coupling stent isrotated so that its axially-oriented struts are out of phase with thoseof the base stent to increase retention therebetween.
 10. The system ofclaim 1, wherein the coupling stent is self-expandable.
 11. The systemof claim 1, wherein the coupling stent is covered with fabric to promotetissue in-growth and/or to reduce paravalvular leakage.
 12. The systemof claim 1, wherein the outflow end of the coupling stent includes aplurality of apertures through which sutures are passed to attach thecoupling stent to the sewing ring.
 13. The system of claim 12, whereinthe outflow end of the coupling stent is defined by a reinforcing ringhaving the plurality of apertures evenly spaced therealong.
 14. Thesystem of claim 1, wherein the sewing ring is undulating and the outflowend of the coupling stent follows an undulating path with alternatingarcuate troughs and peaks so as to conform to the undulating sewingring.
 15. The system of claim 1, wherein the outflow end of the couplingstent includes a continuous reinforcing ring that comprises a series oflengths of struts of fixed length connected by thinner bridge portionsof variable length.
 16. The system of claim 15, wherein the bridgeportions are each formed with a radius so that they can be eitherstraightened or bent more to, respectively, widen or narrow thereinforcing ring.
 17. The system of claim 15, further including a seriesof apertures formed in the reinforcing ring that provide anchor pointsfor sutures when securing the stent to the sewing ring.
 18. The systemof claim 1, wherein the coupling stent has an axial length substantiallythe same as the base stent.
 19. The system of claim 1, wherein thecoupling stent has web-like struts extending between a series ofaxially-extending struts.
 20. The system of claim 19, wherein theoutflow end of the coupling stent defines a plurality of alternatingtroughs and peaks, and wherein at least some of the axially-extendingstruts are in-phase with the peaks and the middle of the troughs. 21.The system of claim 19, wherein the outflow end of the coupling stentdefines a plurality of alternating troughs and peaks, and wherein atleast some of the axially-extending struts are out-of-phase with thepeaks and the middle of the troughs.
 22. The system of claim 1, whereinan outflow end of the coupling stent includes an interrupted reinforcingring comprising a series of short lengths separated by gaps.
 23. Thesystem of claim 22, wherein the outflow end of the coupling stentdefines a plurality of alternating troughs and peaks, with short lengthsof the interrupted reinforcing ring defining the peaks and the middle ofthe troughs.
 24. The system of claim 1, wherein the base stent isexpandable and has a contracted state for delivery to an implantposition adjacent a heart valve annulus and an expanded state sized tocontact and anchor against the heart valve annulus, the base stenthaving a plurality of expandable web-like struts extending between aseries of axially-extending struts, and the coupling stent also having aplurality of expandable web-like struts extending between a series ofaxially-extending struts, and wherein when the coupling stent isexpanded outward into contact with the base stent the coupling stentaxial struts are in-phase with the base stent axial struts.
 25. Thesystem of claim 1, wherein the base stent is expandable and has acontracted state for delivery to an implant position adjacent a heartvalve annulus and an expanded state sized to contact and anchor againstthe heart valve annulus, the base stent having a plurality of expandableweb-like struts extending between a series of axially-extending struts,and the coupling stent also having a plurality of expandable web-likestruts extending between a series of axially-extending struts, andwherein when the coupling stent is expanded outward into contact withthe base stent the coupling stent axial struts are out-of-phase with thebase stent axial struts.